1. Field of the Invention
This invention relates generally to the field of microwave ovens and more particularly to improvements in the food browning units thereof.
2. Description of the Prior Art
It is well known that foods cooked by microwaves do not brown well because of the relatively deep penetration of microwaves into the food. Devices have heretofore been incorporated into microwave ovens which have as their primary function the raising of the surface temperature of the food to a degree higher than that ordinarily achievable by means of microwaves alone in order to brown the food.
The first of these devices, U.S. Pat. No. 3,081,392 to Warner, incorporated a standard electric oven "Cal rod" type resistance heater. Later devices have used additional means, such as mirrors in German Pat. No. 1,049,019, to focus the heat rays on the food. At least one device, U.S. Pat. No. 3,878,350 to Takagi has used a variation on a standard quartz tube. See also U.S. Pat. No. 4,137,442, to Tateda, which is a variable position "Cal rod" type.
A common feature of all these devices is that they substantially intrude into the usable space of the normally small microwave oven cavity.
A second feature of these devices is the multiplication of elements of marginal utility but of great manufacturing expense.
A third feature of many of these devices, especially of those having many elements, is their lack of cleanability. Takagi '350 is a prime example. It incorporates a microwave screen in front of its quartz tubes rendering the device very difficult to clean except by disassembly.
The prior art has had as an object the increase in the surface area heated and planarity to increase uniformity of heating of the food. See Takagi '350. No prior art device has succeeded in this object to the extent of the present invention.